I. Field of the Invention
The invention relates generally to the shattering of earth formations and earth formation removal by the detonation of explosives within boreholes formed in the earth formations. The invention specifically relates to inflatable devices used to support explosives and/or stemming within a borehole and which are configured to be restrained into a first configuration easily insertable into a borehole and subsequently inflatable to expand into a configuration capable of supporting explosives and/or stemming within the borehole.
II. Description of the Prior Art
A practice known as pre-splitting has previously been practiced in mining and earth removal operations. Pre-splitting is used to shatter earth formations in a controllable manner so that subsequent earth removal operations become more efficient. In typical pre-splitting operations, a number of spaced boreholes are drilled in an earth formation which is to be shattered. Explosives are disposed within the boreholes and detonated to shatter the formation. The pre-splitting operation facilitates the removal of overburden by means of subsequent "production" blasting to expose seams of material which is to be mined Earth removal methods used for other purposes also have employed pre-splitting techniques. In both pre-splitting and production blasting, it is desirable to be able to "plug" boreholes with devices capable of supporting heavy columns of explosives and/or stemming materials. Methods and apparatus capable of such use are disclosed in copending U.S. patent applications Ser. No. 166,542 of Mar. 10, 1988 and Ser. No. 276,651 of Nov. 28, 1988, both entitled "Methods and Apparatus for Field Blasting of Earth Formations using Inflatable Devices for Suspending Explosives in Boreholes", the disclosures of both applications being incorporated hereinto by reference. These patent applications describe inflatable devices and methods for their use. The inflatable devices thus disclosed are of substantial utility in the art since they are of simple and inexpensive construction yet are capable of supporting explosives and/or stemming in boreholes of even large diameter.
The art is improved by the provision of the methods and apparatus herein disclosed which provide inexpensive plugging devices which can be rapidly and conveniently used in field blasting operations. The relatively inexpensive nature of the present devices allow the practice of a variety of pre-splitting and blasting methods at a minimum of expense. The present devices and methods thus constitute a significant and substantial advance in the art.